Cisco Systems IPMUX-1E operation manual Frame Format, TDMoIP Frame Structure

Chapter 1 Introduction IPmux-1/1EInstallation and Operation Manual

Frame Format

The Ethernet frame sent by the IPmux-1 is a UDP datagram that transfers E1/T1 payload bytes over IP over Ethernet (UDP payload + UDP header + IP header + Ethernet header). The UDP payload size depends on the connection mode:

•Static mode: The UDP payload size is equal to TDM bytes per frame (TDM bytes/frame configuration).

•Dynamic CAS mode: The maximum UDP payload size depends on the number of configured time slots and is equal to:

[(TSA + 4) x (number of configured timeslots)] + 4] where TSA = Active timeslot bytes in frame

Note Active timeslot bytes in frame are the number of bytes per timeslot that are passed per Ethernet frame.

An Active timeslot is one where a call is detected by monitoring CAS.

The UDP payload size is not fixed–it depends on the number of active time slots:

[(TSA + 4) x (number of active timeslots)] + 4]

•CESoIP mode: The UDP payload size is equal to:

[(Configured Packet Delay) x (number of configured timeslots) x 8] + 12

Table 1-2specifies the structure of the different headers, special fields, and the payload in the Ethernet packet.

MAC

IP

UDP

Payload

Figure 1-15. TDMoIP Frame Structure

1-16 Functional Description